1. Technical Field
The present disclosure relates to Multiprotocol Label Switching and more specifically to verification of Multiprotocol Label Switching contracts by measuring rates of out-of-contract traffic.
2. Introduction
Service Level Agreements (SLA) typically allocate parts of an overall circuit capacity to various Classes of Service (CoSs). For example, in a 40 mbps circuit, an SLA may include 4 mbps in CoS 1, 10 mbps in CoS 2, and 5 mbps in CoS 3. These allocations are called Committed Data Rates (CDRs), referring to the data transfer rates that an Internet Service Provider (ISP) guarantees the virtual circuit will carry.
Routers in the virtual circuit are generally configured to process traffic according to the specified CDRs. Routers are also configured to process excess traffic according to various rules. These rules often depend on the CoS specified for the particular traffic. For example, CoS 1 traffic is given absolute priority for up to 1 mbps, but CoS 1 traffic in excess of 1 mbps is simply discarded. By contrast, excess traffic for other CoSs is not generally dropped, but classified as out-of-contract (or “Drop Eligible”), and forwarded if there is sufficient overall capacity in the virtual circuit.
Because these rules affect the processing of traffic between the customer-edge (CE) router and the provider-edge (PE) router, it is very important that routers are properly configured to apply the rules in accordance with the SLA. Yet it can be extremely difficult to verify that routers are properly configured to process traffic according to the SLA. For example, the customer can schedule time-consuming collaborations with the ISP to verify that the CE router and the PE router are configured correctly. Here, the customer stress tests the CE-PE link while an ISP technician logged into the CE router looks at real-time reports of classifications on the CE router. This can be an expensive and time-consuming process.
A related verification can also be performed by collecting and analyzing flow statistics, which can be used to determine what information is sent to the CE router. However, flow statistics do not present a complete picture, as flow statistics do not provide information regarding how the CE router classifies incoming packets. Thus, without additional information, it is very difficult to determine whether the CE router is improperly classifying packets as out-of-contract, in contravention to the SLA.